A storage device having a flash memory (called “flash device” below) can be rewritten a limited number of times. Therefore, technology is known for extending the useful life of flash devices in the whole of a storage system provided with a plurality of flash devices, by moving data between the flash devices (PTL 1).
In a storage system, if access operations are concentrated in any one of the storage devices, the performance of the storage device creates a bottleneck in the whole storage system. Therefore, technology is known for preventing the occurrence of bottlenecks of this kind by moving data between storage devices in a storage system.
Technology is also known for equalizing the consumed amount of storage capacity between storage devices, by moving data between storage devices, in a storage system (PTL 2).